Non-resonant magnetic resonance coil and magnetic resonance imaging system using the same

ABSTRACT

A magnetic resonance coil and a magnetic resonance imaging system using the same are provided. The magnetic resonance coil may include an antenna, an amplifier, and a protective circuit. The antenna may be configured to receive a radio frequency (RF) signal emitted from an object. The antenna may not resonate with the RF signal. The amplifier operably coupled to the antenna configured to amplify the RF signal. The protective circuit may be configured to protect the antenna and the amplifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/098,502, filed on Nov. 16, 2020, which is a continuation-in-part ofU.S. patent application Ser. No. 16/750,013, filed on Jan. 23, 2020, nowU.S. Pat. No. 10,838,027, which is a continuation of U.S. patentapplication Ser. No. 15/856,058, filed on Dec. 28, 2017, now U.S. Pat.No. 10,545,204, which claims priority of Chinese Patent Application No.201710581577.X, filed on Jul. 17, 2017, Chinese Patent Application No.201710582369.1, filed on Jul. 17, 2017, and Chinese Patent ApplicationNo. 201710582372.3, filed on Jul. 17, 2017, the contents of each ofwhich are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to a radio frequency (RF) coil,and more particularly, to an RF coil implemented in a magnetic resonanceimaging system for receiving an RF signal emitted from an object.

BACKGROUND

Magnetic resonance imaging (MRI) is an imaging technique used inradiology to form images of the anatomy and the physiological processesof an object (e.g., a patient, or a section thereof). MRI scanners usestrong magnetic fields, radio waves, and field gradients to generateimages of the inner structure of the object based on the science ofnuclear magnetic resonance (NMR). More particularly, certain atomicnuclei (e.g., hydrogen-1, carbon-13, oxygen-17, etc.) absorb and emit RFenergy when placed in an external magnetic field. The emitted RF energyexists as RF signals and is received by the MRI scanners.

Hydrogen atoms are often used to generate a detectable RF signal that isreceived by an antenna of a coil in close proximity to the object beingexamined. Conventionally, the antenna includes capacitance, conductance,and/or resistance that provide the antenna a specific resonantfrequency. When the frequency of the RF signal emitted from the objectmatches the resonant frequency of the antenna, the antenna resonates andreceives the RF signal. Hence, the antenna has to be designed carefullyso that the resonant frequency exactly matches the frequency of the RFsignal emitted from the object. However, the antenna is usually deformed(bent) in use and the resonant frequency changes. When the resonantfrequency no longer matches the frequency of the RF signal emitted fromthe object, the coil does not work as well as before and the RF signalis received at a lower quality (e.g., with a lower signal-to-noise ratio(SNR)). Therefore, it is desired to develop a coil that is able toreceive the RF signal even when it is deformed.

In addition, during an MRI scan, a transmitting coil of an MRI devicemay transmit an RF excitation pulse to an object, and a magneticresonance coil (e.g., an antenna) of the MRI device may receive an RFsignal excited by the RF excitation pulse from the object. An RF-inducedvoltage may be caused by the RF excitation pulse and applied to themagnetic resonance coil, which may cause damage to the magneticresonance coil (e.g., an amplifier of the magnetic resonance coil)and/or the object (e.g., the magnetic resonance coil may become hot dueto the RF-induced voltage). Therefore, it is desired to develop aprotection circuit to protect the magnetic resonance coil.

SUMMARY

In an aspect of the present disclosure, a magnetic resonance coil isprovided. The magnetic resonance coil may include an antenna configuredto receive a radio frequency (RF) signal emitted from an object, whereinthe antenna does not resonate with the RF signal. The magnetic resonancecoil may further include a signal processor coupled to the antennaconfigured to process the RF signal to generate a processed signal.

In some embodiments, the antenna is a non-resonant antenna.

In some embodiments, the antenna may be made of one or more deformableconductive materials.

In some embodiments, the antenna may be a birdcage structure configuredto receive the RF signal from an entire body of the object.

In some embodiments, the antenna may be a loop structure configured toreceive the RF signal from a portion of the object.

In some embodiments, the signal processor may include an amplifiercoupled to the antenna and configured to amplify the RF signal.

In some embodiments, the amplifier is a differential amplifier.

In some embodiments, the magnetic resonance coil may further include amatching circuit coupled between the antenna and the amplifier andconfigured to match an impedance of the antenna and an impedance of theamplifier.

In some embodiments, the matching circuits is a broadband matchingcircuit that matches the impedance of the antenna and the impedance ofthe amplifier over a frequency range of the broadband signals.

In some embodiments, the magnetic resonance coil may further include anadjusting circuit coupled to the amplifier and configured to adjust themagnitude of the imaginary part of impedance of the amplifier.

In some embodiments, the adjusting circuit may include at least one of avariable capacitor or a variable conductor.

In some embodiments, the signal processor may further include a filtercoupled to the amplifier.

In some embodiments, the signal processor may further include aheterodyne receiver or a homodyne receiver coupled to the amplifier.

In some embodiments, the signal processor is a direct samplingstructure, and the signal processor may include an analog-to-digitalconverter configured to convert the RF signal to a digital signal.

In some embodiments, the antenna may be configured without capacitiveelements on conductive materials.

In some embodiments, the antenna may be configured with no impedancematching circuit.

In some embodiments, the amplifier may be configured with an inputimpedance greater than 500 Ohms.

In some embodiments, the antenna may be configured with no couplingunit, nor decoupling unit.

In some embodiments, the magnetic resonance coil may be implemented in amulti-nuclear magnetic resonance system relating to a plurality ofatomic nuclei. The plurality of atomic nuclei may include phosphorusatom or sodium atom.

In another aspect of the present disclosure, a magnetic resonanceimaging (MRI) system is provided. The MRI system may include a mainelectromagnet configured to generate a uniform magnetic field on anobject, and a gradient electromagnet configured to generate a gradientmagnetic field on the object. The MRI system may further include atransmitting coil configured to transmit a first radio frequency (RF)signal to the object, and a receiving coil configured to receive andprocess a second RF signal emitted from the object in response to thefirst RF signal. The receiving coil may include an antenna configured toreceive a radio frequency (RF) signal emitted from an object, whereinthe antenna does not resonate with the RF signal. The receiving coil mayfurther include a signal processor coupled to the antenna configured toprocess the RF signal to generate a processed signal. The MRI system mayinclude a processor configured to generate an image of the object basedon the processed signal. The MRI system may include a display configuredto display the generated image of the object.

In another aspect of the present disclosure, a magnetic resonance coilis provided. The magnetic resonance coil may include an antennaconfigured to receive a radio frequency (RF) signal emitted from anobject. The antenna may not resonate with the RF signal. The magneticresonance coil may also include an amplifier operably coupled to theantenna configured to amplify the RF signal. The magnetic resonance coilmay further include a protective circuit configured to protect theantenna and the amplifier.

In some embodiments, an input impedance of the amplifier may be greaterthan 500 Ohms.

In some embodiments, an input impedance of the antenna may besubstantially equal to an input impedance corresponding to an optimalnoise factor of the amplifier.

In some embodiments, an impedance of the protective circuit may begreater than an input impedance of the amplifier.

In some embodiments, the protective circuit may include a protectivecapacitor. The protective circuit may also include a protective inductorin parallel with the protective capacitor. The protective circuit mayfurther include a control device configured to actuate the protectivecircuit when an actuation condition is satisfied.

In some embodiments, the control device may include a switch in serieswith the protective inductor and a control component configured tocontrol the switch.

In some embodiments, the switch may include at least one of a radiofrequency (RF) diode, a PIN diode, a micro-electromechanical system(MEMS) switch, or a field-effect transistor (FET) switch.

In some embodiments, the control device may include a pair ofanti-parallel diodes in series with the protective inductor.

In some embodiments, the antenna may have an antenna inductance and aload resistance. An impedance of the protective capacitor may be smallerthan an impedance of the antenna inductance.

In some embodiments, the impedance of the protective capacitor may besmaller than 1/10 of the impedance of the antenna inductance.

In some embodiments, the protective circuit may include a sub-protectivecircuit configured to protect the amplifier when a current passingthrough the amplifier exceeds a threshold current.

In some embodiments, the sub-protective circuit may include a pair ofanti-parallel diodes in parallel with the amplifier.

In some embodiments, an impedance of the protective circuit may bedetermined based on an intensity of an RF field at the antenna, anangular frequency of an RF excitation pulse, and a size of the antenna.

In some embodiments, the antenna may be a non-resonant antenna.

In another aspect of the present disclosure, a magnetic resonance coilis provided. The magnetic resonance coil may include a plurality ofantenna units. At least one antenna unit of the plurality of antennaunits may include an antenna configured to receive a radio frequency(RF) signal emitted from an object, wherein the antenna does notresonate with the RF signal. At least one antenna unit of the pluralityof antenna units may also include an amplifier operably coupled to theantenna configured to amplify the RF signal. At least one antenna unitof the plurality of antenna units may further include a protectivecircuit configured to protect the antenna and the amplifier. When theprotective circuit is activated, an impedance of the protective circuitmay be smaller than an impedance of the antenna. When the protectivecircuit is deactivated, the impedance of the protective circuit may begreater than an input impedance of the amplifier.

In some embodiments, the plurality of antenna units may include that atleast one pair of antenna units that overlap with each other.

In some embodiments, the plurality of antenna units may include at leastone movable antenna unit.

In still another aspect of the present disclosure, a method forcontrolling a magnetic resonance coil is provided. The magneticresonance coil may include an antenna configured to receive a radiofrequency (RF) signal emitted from an object and an amplifier operablycoupled to the antenna configured to amplify the RF signal. The antennamay not resonate with the RF signal. The method may include couplingeach of the antenna and the amplifier with a protective circuit. Themethod may further include operating the protective circuit to protectthe antenna and the amplifier when the antenna receives the RF signal.When the protective circuit is activated, an impedance of the protectivecircuit may be smaller than an impedance of the antenna. When theprotective circuit is deactivated, the impedance of the protectivecircuit may be greater than an input impedance of the amplifier.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting examples,in which like reference numerals represent similar structures throughoutthe several views of the drawings, and wherein:

FIG. 1 is a schematic block diagram of an exemplary magnetic resonanceimaging (MRI) system according to some embodiments of the presentdisclosure;

FIG. 2 is a flowchart illustrating an exemplary process for processingan RF signal according to some embodiments of the present disclosure;

FIG. 3 is a flowchart illustrating an exemplary process for processingan RF signal according to some embodiments of the present disclosure;

FIG. 4 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure;

FIG. 5 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure;

FIG. 6 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure;

FIG. 7 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure;

FIG. 8 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure;

FIG. 9 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure;

FIG. 10 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure;

FIG. 11 is a schematic diagram illustrating an exemplary amplifyingcircuit according to some embodiments of the present disclosure;

FIG. 12 is a schematic diagram illustrating an exemplary double terminalnetwork according to some embodiments of the present disclosure.

FIG. 13A is a schematic diagram illustrating a conventional magneticresonance coil;

FIGS. 13B and 13C illustrate conventional arrangements of coil unitswith a circular shape;

FIG. 13D illustrates a conventional arrangement of coil units with asquare shape;

FIG. 14 is a schematic block diagram of an exemplary magnetic resonancecoil according to some embodiments of the present disclosure;

FIG. 15 is a schematic diagram illustrating an exemplary magneticresonance coil according to some embodiments of the present disclosure;

FIG. 16 is a schematic diagram illustrating an exemplary magneticresonance coil according to some embodiments of the present disclosure;

FIG. 17 is a schematic diagram illustrating an exemplary magneticresonance coil according to some embodiments of the present disclosure;

FIG. 18A is a schematic diagram illustrating an exemplary magneticresonance coil according to some embodiments of the present disclosure;and

FIG. 18B is a schematic diagram illustrating an exemplary magneticresonance coil according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well-known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirits andscope of the present disclosure. Thus, the present disclosure is notlimited to the embodiments shown, but to be accorded the widest scopeconsistent with the claims.

It will be understood that the term “system,” “unit,” “module,” and/or“block” used herein are one method to distinguish different components,elements, parts, section or assembly of different level in ascendingorder. However, the terms may be displaced by another expression if theymay achieve the same purpose.

It will be understood that when a unit, module or block is referred toas being “on,” “connected to” or “coupled to” another unit, module, orblock, it may be directly on, connected or coupled to the other unit,module, or block, or intervening unit, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

The terminology used herein is for the purposes of describing particularexamples and embodiments only, and is not intended to be limiting. Asused herein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “include,”and/or “comprise,” when used in this disclosure, specify the presence ofintegers, devices, behaviors, stated features, steps, elements,operations, and/or components, but do not exclude the presence oraddition of one or more other integers, devices, behaviors, features,steps, elements, operations, components, and/or groups thereof.

The present disclosure provides a magnetic resonance coil implemented inan MRI system. The present magnetic resonance coil may receive an RFsignal generated by an object being examined even when it is deformed.The magnetic resonance coil may include an antenna that does notresonate with the RF signal and a signal processor coupled to theantenna configured to process the RF signal. In some embodiments,different atoms may emit RF signals at different frequencies. As thenon-resonant RF antenna may receive RF signals at a wide range offrequencies, it may be used to image atoms, such as a phosphorus atom, asodium atom, etc. besides the atoms that are commonly imaged in an MRIsystem (e.g., hydrogen atoms, carbon atoms, oxygen atoms). The antennamay be a birdcage structure configured to receive the RF signal from anentire body of the object or may be a loop structure configured toreceive the RF signal from a portion of the object. The signal processormay be an analog signal processor or a digital signal processor. Thesignal processor may include an amplifier configured to amplify thereceived RF signal. The magnetic resonance coil may include an adjustingcircuit configured to adjust the magnitude of the imaginary part ofimpedance of the amplifier. The input impedance of the amplifier may begreater than 500 Ohms.

The present disclosure further provides another magnetic resonance coilimplemented in an MRI system. The magnetic resonance coil may include anantenna, an amplifier, and a protective circuit. The antenna may beconfigured to receive an RF signal emitted from an object. The antennamay not resonate with the RF signal. The amplifier may be configured toamplify the RF signal. The protective circuit may be configured toprotect the antenna and the amplifier. For example, when the protectivecircuit is activated, the impedance of the protective circuit may besmaller than the impedance of the antenna, such that the antenna mayremain in a non-resonant state. Additionally or alternatively, when theprotective circuit is deactivated, the impedance of the protectivecircuit may be greater than an input impedance of the amplifier. In theactivated cases, a greater portion of an RF-induced voltage may beapplied to the protective circuit than the amplifier so that theamplifier may be protected.

In some embodiments, the above mentioned antenna unit (which includesthe antenna, the amplifier, and the protective circuit) can be furtherused to create an array of antenna units to receive magnetic resonancesignals. Compared with a conventional magnetic resonance coil whichneeds to adopt a decoupling mechanism for adjacent antenna units, themagnetic resonance coil including the array of antenna units disclosedin the present disclosure may have an improved layout flexibility andsafety.

FIG. 1 is a schematic block diagram of an exemplary magnetic resonanceimaging (MRI) system 100 according to some embodiments of the presentdisclosure. As shown in FIG. 1, the MRI system 100 may include an MRIscanner 130, a computing device 140, a processing engine 122, and astorage device 125. It should be noted that the imaging system describedbelow is merely provided for illustration purposes, and not intended tolimit the scope of the present disclosure. The MRI system 100 may findits applications in various fields, such as healthcare industries (e.g.,medical applications), security applications, industrial applications,etc. For example, the MRI system 100 may be used for analyzingcomposition of a specimen, nuclear magnetic resonance logging, or thelike, or a combination thereof.

The MRI scanner 130 may include a main magnet 101, a gradient magnet102, a volume coil 103, a local coil 104, a scanning bed 106, an pulsecontroller 111, a gradient signal generator 112, a first gradientamplifier 113, a second gradient amplifier 114, a third gradientamplifier 115, an RF pulse generator 116, a switch 117, and an RF signalreceiver 118. A detecting region 105 may be formed in the MRI scanner130. The detecting region 105 may be a place where the object is scannedby the MRI scanner 130.

The MRI scanner 130 may be configured to scan an imaging object 150. TheMRI scanner 130 may obtain information related to the imaging object 150by scanning the imaging object 150. More particularly, certain atomicnuclei (e.g., hydrogen-1, carbon-13, oxygen-17, etc.) may absorb andemit RF energy when being placed in the main magnetic 101 and thegradient magnet 102. The emitted RF energy exists as RF signals and isreceived by the MRI scanner 130. The MRI scanner 130 may reconstruct adistribution of the atomic nuclei inside the imaging object based on theRF signals as an MRI image.

The main magnet 101 may be placed in a gantry 145 of the MRI scanner.The main magnet 101 may be configured to generate a uniform mainmagnetic field. The strength of the main magnetic field may be 0.2Tesla, 0.5 Tesla, 1.0 Tesla, 1.5 Tesla, 3.0 Tesla, etc. In someembodiments, the main magnet 101 may be a superconducting coil.Alternatively, the main magnet 101 may be a permanent magnet.

The scanning bed 106 may support the imaging object 150 during a scan.The object may be biological or non-biological. Merely by way ofexample, the object may include a patient, an organ, a specimen, aman-made object, a mold, etc. During a scan, the imaging object 150 maybe supported and delivered to the detecting region 105 of the gantry 145by the scanning bed 106. The detecting region 105 may be a region thatthe magnetic field distribution of the main magnetic field is relativelyuniform, and to which, the RF signal is transmitted.

Merely by way of example, a spatial coordinate system (i.e., acoordinate system of the MRI scanner) may be described relative to thegantry 145 of the MRI scanner 130. For example, a Z axis may be thedirection along the axis of the gantry, an X axis and a Y axis may bethe directions perpendicular to the Z axis. The long-axis direction ofthe imaging object may coincide with the direction of the Z axis and thescanning bed 106 may move in the direction of the Z axis.

The pulse controller 111 may be configured to control the generation ofRF signals. For example, the pulse controller 111 may control the RFpulse generator 116 and the gradient signal generator 112. In someembodiments, the pulse controller 111 may control the RF pulse generator116 to generate an RF pulse. The RF pulse may be amplified by anamplifier. In some embodiments, the pulse controller 111 may control thegradient signal generator 112 to generate gradient signals.

The pulse controller 111 may receive information from or sendinformation to the MRI scanner, the processing engine 122, and/or adisplay 123. According to some embodiments of the present disclosure,the pulse controller 111 may receive a command from a user via thedisplay 123 and control components of the MRI scanner (e.g., the RFpulse generator 116) accordingly to start a scan.

The RF pulse generator 116 may generate an RF pulse. In someembodiments, the RF pulse generator 116 may generate the RF pulse basedon an instruction from the pulse controller 111. The RF pulse may beamplified by an amplifier. The switch 117 may be configured to controlthe emission of the amplified RF pulse. For example, the amplified RFpulse may be emitted by the volume coil 103 and/or the local coil 104when the switch 117 is on. The emitted RF pulse may excite the atomicnuclei in the imaging object 150. The imaging object 150 may generate acorresponding RF signal when the RF excitation is removed. The volumecoil 103 and/or the local coil 104 may transmit RF signals to or receiveRF signals from the imaging object 150. For example, the volume coil 103and/or the local coil 104 may transmit the amplified RF pulse to theimaging object 150. For another example, the volume coil 103 and/or thelocal coil 104 may receive the RF signal emitted from the imaging object150. In some embodiments, the volume coil 103 and/or the local coil 104may include a plurality of RF receiving channels. The plurality of RFreceiving channels may transmit RF signals received from the imagingobject 150 to the RF signal receiver 118. In some embodiments, thevolume coil 103 may be configured to transmit RF signals to or receiveRF signals from the entire body of the imaging object 150 while thelocal coil 104 may be configured to transmit RF signals to or receive RFsignals from a portion of the imaging object 150.

The volume coil 103 and/or the local coil 104 may bemagnetically-insulated. In some embodiments, the volume coil 103 and thelocal coil 104 are non-resonant coils which do not include anycapacitance. The volume coil 103 and/or the local coil 104 may be madeof one or more deformable materials. For example, the volume coil 103and/or the local coil 104 may be made of shape-memory alloy. Theshape-memory alloy may recover to its original shape under a recoveringcondition (e.g., a high temperature, a large strain). The shape-memoryalloy may include silver, cadmium, gold, nickel, titanium, hafnium,copper, zinc, or the like, or any combination thereof. For anotherexample, the volume coil 103 and/or the local coil 104 may be made ofdeformable conductive materials. The deformable conductive materials mayinclude metallic materials such as solid metals, alloys, liquid metals,etc. The liquid metals may include mercury, aluminum, cesium, gallium,rubidium, or the like, or any combination thereof.

In some embodiments, the volume coil 103 may be a large coil (e.g., abirdcage coil) that can accommodate the entire body of the imagingobject 150. The local coil 104 may be a small coil (e.g., a loop coil, asolenoid coil, a saddle coil, a flexible coil, etc.) that covers aportion of the imaging object 150.

The RF signal receiver 118 may be configured to receive RF signals. TheRF signal receiver 118 may receive RF signals from the volume coil 103and/or the local coil 104.

The gradient signal generator 112 may generate gradient signals. In someembodiments, the gradient signal generator 112 may generate gradientsignals based on an instruction from the pulse controller 111. Thegradient signals may include three orthogonal signals. In someembodiments, the three orthogonal signals may be a first gradient signalalong the X direction, a second gradient signal along the Y direction,and a third gradient signal along the Z direction. The gradient signalsmay help to locate the atomic nuclei.

The first gradient amplifier 113, the second gradient amplifier 114, andthe third gradient amplifier 115 may be configured to amplify thegradient signals generated by the gradient signal generator 112. Inparticular, the first gradient amplifier 113 may amplify the firstgradient signal, the second gradient amplifier 114 may amplify thesecond gradient signal, and the third gradient amplifier 115 may amplifythe third gradient signal, respectively.

The gradient magnet 102 (also called gradient coil 102) may beconfigured to spatially encode RF signals (e.g., an RF pulse generatedby the RF pulse generator 116). The gradient magnet 102 may generate amagnetic field with a strength less than that of the main magneticfield. For example, the gradient magnet 102 may generate a gradientmagnet field in the detecting region 105.

In some embodiments, the MRI scanner 130 may include both a volume coil103 and a local coil 104. For example, the volume coil 103 may beconfigured to emit RF signals, and the local coil may be configured toreceive RF signals, or vice versa. The volume coil 103 and the localcoil 104 may each include an amplifier with a high input impedancevalue, respectively. The amplifiers with high input impedance maydecouple the volume coil and the local coil without additionaldecoupling methods.

The computing device 140 may include a reconstruction module 121, thedisplay 123, an input/output (I/O) 124, and a communication port 126.

The reconstruction module 121 may be configured to reconstruct an MRIimage. The reconstruction module 121 may reconstruct an MRI image basedon RF signals received by the RF signal receiver 118.

The display 123 may be configured to display images. The display 123 mayinclude a liquid crystal display (LCD), a light emitting diode(LED)-based display, or any other flat panel display, or may use acathode ray tube (CRT), a touch screen, or the like. A touch screen mayinclude, e.g., a resistor touch screen, a capacity touch screen, aplasma touch screen, a vector pressure sensing touch screen, an infraredtouch screen, or the like, or a combination thereof.

The I/O 124 may input and/or output signals, data, information, etc. Theinput and/or output information may include programs, software,algorithms, data, text, number, images, voice, or the like, or anycombination thereof. For example, a user or an operator may input someinitial parameters or conditions to initiate a scan. As another example,some information may be imported from an external resource, such as afloppy disk, a hard disk, a wireless terminal, or the like, or anycombination thereof. In some embodiments, the I/O 124 may enable a userinteraction with the processing engine 122. In some embodiments, the I/O124 may include an input device and an output device. Examples of theinput device may include a keyboard, a mouse, a touch screen, a controlbox, a microphone, or the like, or a combination thereof. Examples ofthe output device may include a display device, a loudspeaker, aprinter, a projector, or the like, or a combination thereof.

The communication port 126 may be connected to a network (not shown) tofacilitate data communications. The communication port 126 may establishconnections between an external device, an image acquisition device, adatabase, an external storage, and an image processing workstation, etc.The connection may be a wired connection, a wireless connection, anyother communication connection that can enable data transmission and/orreception, and/or any combination of these connections. The wiredconnection may include, for example, an electrical cable, an opticalcable, a telephone wire, or the like, or any combination thereof. Thewireless connection may include, for example, a Bluetooth™ connection, aWi-Fi™ connection, a WiMax™ connection, a WLAN connection, a ZigBeeconnection, a mobile network connection (e.g., 3G, 4G, 5G, etc.), or thelike, or a combination thereof. In some embodiments, the communicationport 126 may include a standardized communication port, such as RS232,RS485, etc. In some embodiments, the communication port 126 may be aspecially designed communication port. For example, the communicationport 126 may be designed in accordance with the digital imaging andcommunications in medicine (DICOM) protocol.

The processing engine 122 may process different kinds of information.For example, the processing engine 122 may process RF signals receivedfrom the RF signal receiver 118 to the reconstruction module 121 togenerate one or more images based on these signals and sent the imagesto the display 123. In some embodiments, the processing engine 122 mayprocess data input by a user or an operator via the display 123 and/orthe I/O 124, transform the data into specific commands, and supply thecommands to the pulse controller 111. The processing engine 122 mayinclude one or more processors.

The storage device 125 may store data relating to the MRI system 100.The data may be data files related to processing and/or communication,program command to be executed by the processor engine 112, a numericalvalue, an image, information of an object, an instruction and/or asignal to operate the MRI system 100, voice, a model relating to apatient, an algorithm relating to an image processing technique, or thelike, or a combination thereof. Exemplary numerical values may include athreshold, a MR value, a value relating to a coil, or the like, or acombination thereof. Exemplary images may include a raw image or aprocessed image (e.g., an image after pretreatment). Exemplary modelsrelating to a patient may include the background information of thepatient, such as, ethnicity, citizenship, religion, gender, age,matrimony state, height, weight, medical history (e.g., history relatingto different organs, or tissues), job, personal habits, or the like, ora combination thereof.

The storage device 125 may include a random access memory (RAM), aread-only memory (ROM), or the like, or a combination thereof. Therandom access memory (RAM) may include a dekatron, a dynamic randomaccess memory (DRAM), a static random access memory (SRAM), a thyristorrandom access memory (T-RAM), a zero capacitor random access memory(Z-RAM), or the like, or a combination thereof. The read only memory(ROM) may include a bubble memory, a magnetic button line memory, amemory thin film, a magnetic plate line memory, a core memory, amagnetic drum memory, a CD-ROM drive, a hard disk, a flash memory, orthe like, or a combination thereof. The storage device 125 may be aremovable storage device such as a chip disk that may read data fromand/or write data to the reconstruction module 121 in a certain manner.The storage device 125 may also include other similar means forproviding computer programs or other instructions to operate themodules/units in the MRI system 100. The storage device 125 may beoperationally connected to one or more virtual storage resources (e.g.,a cloud storage, a virtual private network, other virtual storageresources, etc.) for transmitting or storing the data into the one ormore virtual storage resources.

In some embodiment, the pulse controller 111, the reconstruction module121, the processing engine 122, the display 123, the I/O 124, thestorage device 125, and the communication port 126 may transmit data toeach other via a communication bus 127 to control an imaging process ofthe MRI scanner 130.

This description is intended to be illustrative, and not to limit thescope of the present disclosure. Many alternatives, modifications, andvariations will be apparent to those skilled in the art. The features,structures, methods, and other characteristics of the exemplaryembodiments described herein may be combined in various ways to obtainadditional and/or alternative exemplary embodiments. For example, thestorage device 125 may be a database including cloud computingplatforms, such as a public cloud, a private cloud, a community andhybrid clouds, etc. As another example, the pulse controller 111, theprocessing engine 122, and/or the display 123 may be integrated into anMRI console (not shown). Users may set parameters in MRI scanning,control the imaging procedure, view the images produced through the MRIconsole. However, those variations and modifications do not depart thescope of the present disclosure.

FIG. 2 is a flowchart illustrating an exemplary process for processingan RF signal according to some embodiments of the present disclosure. Insome embodiments, a process 300 may be implemented in the MRI system 100as illustrated in FIG. 1.

In 202, an RF signal emitted from an object may be received by an RFreceiving coil. The RF receiving coil may be a non-resonant coil. Theobject may be biological or non-biological. Merely by way of example,the object may include a patient, an organ, a specimen, a man-madeobject, a mold, etc. The RF signal may be an analog signal or a digitalsignal. As mentioned in FIG. 1, the object may be placed in a magneticfield and a volume coil 103 and/or a local coil 104 may transmit an RFsignal to the object. The transmitted RF signal may excite atomic nucleiin the imaging object 150. The imaging object 150 may generate acorresponding RF signal when the RF excitation is removed. The objectmay emit the RF signal based on relaxation properties of atomic nucleitherein. The atomic nuclei may include hydrogen-1, carbon-13, oxygen-17,sodium 23, phosphorus-31, or the like, or any combination thereof.

In 204, the received RF signal may be processed to generate a processedsignal. In some embodiments, the processing engine 122 may first processthe RF signal and then convert the processed RF signal to a digitalsignal. For example, the processing engine 122 may amplify the RFsignal, filter the amplified RF signal to generate a processed RFsignal, and then convert the processed RF signal to a digital signal. Insome embodiments, the processing engine 122 may convert the RF signal toa digital RF signal before processing the signal. For example, ananalog-to-digital converter may be configured to convert the RF signalto a digital signal. Digital signal processing may include procedures ofsignal amplification, frequency conversion, filtering, notch, or thelike, or any combination thereof.

FIG. 3 is a flowchart illustrating an exemplary process for processingan RF signal according to some embodiments of the present disclosure. Insome embodiments, the process 300 may be implemented in the MRI system100 as illustrated in FIG. 1.

In 302, an RF signal emitted from an object may be received by an RFreceiving coil (e.g., volume coil 103, local coil 104, etc.). The RFreceiving coil may be a non-resonant coil. The object may be biologicalor non-biological. Merely by way of example, the object may include apatient, an organ, a specimen, a man-made object, a mold, etc. The RFsignal may be an analog signal or a digital signal. As mentioned in FIG.1, the object may be placed in a magnetic field and a volume coil 103and/or a local coil 104 may transmit an RF signal to the object. Thetransmitted RF signal may excite atomic nuclei in the imaging object150. The imaging object 150 may generate a corresponding RF signal whenthe RF excitation is removed. The object may emit the RF signal based onrelaxation properties of atomic nuclei therein. The atomic nuclei mayinclude hydrogen-1, carbon-13, oxygen-17, sodium 23, phosphorus-31, orthe like, or any combination thereof.

In some embodiments, the RF signal may be an analog signal. The RFsignal may be converted to a digital signal before further processing(see, e.g., step 304 to step 308). In some embodiments, the RF signalmay be processed before converted to a digital signal (see, e.g., step310 to step 312).

In 304, the RF signal may be amplified. The processing engine 122 maycontrol an amplifier to amplify the RF signal. The amplifier may becoupled to the RF receiving coil. The amplifier may be a low noiseamplifier. The low noise amplifier may be a component of an analogsignal processor (e.g., an analog signal processor 403). In someembodiments, a matching circuit (e.g., a matching circuit 1003) may beconfigured to match an impedance of the RF receiver with an impedance ofthe amplifier.

In 306, the amplified RF signal may be filtered to generate a filteredsignal. The processing engine 122 may control a filter to filter theamplified RF signal. In some embodiments, the filter may be coupled toan amplifier directly. For example, a low-pass filter may be directlyconnected to the amplifier and filter the amplified RF signal. In someembodiments, the filter may be coupled to a down converter coupled tothe amplifier. For example, the filter may be a channel selection filter(or a bandpass filter) coupled to a down converter. In some embodiments,the filer may be a portion of an analog signal processor.

In 308, the filtered signal may be converted to a digital signal. Theprocessing engine 122 may control an analog-to-digital converter (e.g.,an analog-to-signal converter 903) to convert the filtered signal to adigital signal. In some embodiments, the analog-to-digital converter maybe coupled to an analog signal processor.

In 310, the RF signal may be converted to a digital signal. The RFsignal may be an analog signal. The processing engine 122 may control ananalog-to-digital converter to convert the RF signal to a digitalsignal. The analog-to-digital converter may be coupled to an RFreceiving coil directly.

In 312, the digital signal may be processed. The processing engine 112may control a digital signal processor to process the digital signal.The digital processor may be coupled to the analog-to-digital converter.The signal processing may include procedures of signal amplification,frequency conversion, filtering, notch, or the like, or any combinationthereof.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, other analog or digital signal processing methods may beadded or may replace the current operations in the process 300.

FIG. 4 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure. As shown, the magnetic resonance RF coil 400 may include anRF antenna 401, a matching circuit 402, an analog signal processor 403,an analog-to-digital converter 404, a controlling circuit 405, and anenergy supplying circuit 406. It should be noted that the magneticresonance RF coil described herein is merely provided for illustrativepurposes, and not intended to limit the scope of the present disclosure.The magnetic resonance RF coil 400 may find its applications in variousfields, such as healthcare industries (e.g., medical applications),security applications, industrial applications, etc. For example, themagnetic resonance RF coil 400 may be used for internal inspections ofcomponents including, e.g., flaw detection, security scanning, failureanalysis, metrology, assembly analysis, void analysis, wall thicknessanalysis, or the like, or a combination thereof.

The RF antenna 401 may be configured to receive RF signals from anobject (e.g., the imaging object 150). In some embodiments, the RFantenna 401 may be a non-resonant RF antenna. For example, the RFantenna 401 may not include any capacitive components and may notresonant at a fixed frequency. Instead, the RF antenna 401 may beconfigured to resonant and receive signals at a wide range offrequencies (broadband signals). Merely by way of example, an antenna ofa 1.5 T MRI system that includes capacitance may resonant at a frequencyfixed at, for example, about 64 MHz. However, the RF antenna 401 mayresonant at a frequency range, e.g., from 57 MHz to 74 MHz. Besides theatoms that are commonly imaged in an MRI system (e.g., hydrogen atoms,carbon atoms, oxygen atoms), the non-resonant RF antenna 401 may be usedto image atoms, such as a phosphorus atom, a sodium atom, etc. The RFantenna 401 may be in a structure of a loop, a solenoid, a saddle, orthe like.

The matching circuit 402 may be electrically connected to the RF antenna401. The matching circuit 402 may be configured to match the impedanceof the RF antenna 401 and that of the analog signal processor 403 toreduce the noise generated in the RF coil 400. In some embodiments, thematching circuit 402 may be a broadband matching circuit which may matchthe impedance of the radio frequency antenna 401 and the analog signalprocessor 403 over a frequency range of the broadband signals.

The analog signal processor 403 may be electrically coupled to thematching circuit 402. The analog signal processor 403 may be configuredto process an analog signal received by the RF antenna 401. For example,the signal process may include procedures of sampling, analog signalamplification, filtering, phase shifting, notch, or the like, or acombination thereof.

The analog-to-digital converter 404 may be configured to convert ananalog signal to a digital signal. The analog-to-digital converter 404may be configured to pre-process the digital signal. For example, theanalog-to-digital converter 404 may compress a digital signal. Foranother example, the analog-to-digital converter 404 may adjust adigital signal. The analog-to-digital converter 404 may be connected toa cable, a fiber optic or a wireless means, via which the digital signalis to be transmitted.

The controlling circuit 405 may be configured to control the analogsignal processor 403 and the analog-to-digital converter 404. Thecontrolling circuit 405 may include a timing circuit with a clocksignal. The clock signal may be configured to control ananalog-to-digital sampling in the analog-to-digital converter 404. Theclock signal may also control the RF coil 401 regarding the acquisitionof RF signals.

The energy supplying circuit 406 may be configured to transmitelectrical power (energy) to the analog signal processor 403 and theanalog-to-digital converter 404. The energy supplying circuit 406 mayinclude a battery pack. The battery pack may supply power to the analogsignal processor 403 and the analog-to-digital converter 404. In someembodiments, the energy supplying circuit 406 may be configured tosupply power to circuits other than analog signal processor 403 and theanalog-to-digital converter 404 of the RF coil 400. For example, theenergy supplying circuit 406 may supply power to the controlling circuit405. In some embodiments, the energy supplying circuit 306 may berechargeable. The energy supplying circuit 406 may be recharged by e.g.,a portable power supply, a direct current (DC) cable or a wirelesscharging device.

In some embodiments, the RF antenna 401 may be a non-resonant antennaand the low noise amplifier may be configured with a high inputimpedance value. Conventionally, a coupling circuit may be configured toresonate at a center frequency, and a decoupling circuit may beconfigured to maintain a receiving coil in a non-working state when atransmitting coil is emitting signals. Due to the high input impedanceof the low noise amplifier, coupling/decoupling circuits between coilsof the RF antenna may be removed, and a signal to noise ratio of RFsignals may be improved. Also due to the high input impedance of the lownoise amplifier, a matching network for matching the input impedance ofan RF antenna and the coupling circuit may be omitted.

In some embodiments, the low noise amplifier with a high input impedancevalue may be configured to receive and output differential signals,avoiding the generation of common-mode signals during signaltransmissions. The common-mode signals may cause unwanted coupling andsignal-to-noise ratio (SNR) loss. The coils may be the volume coils 103,the local coils 104, the gradient coil 102, or the like, or acombination thereof.

FIG. 5 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure. Asshown in FIG. 5, the analog signal processor 500 may include a low noiseamplifier 501 and a filter 502.

The analog signal processor 500 may be configured to amplify and filteran RF signal received from the RF antenna 401. The low noise amplifier501 may directly sample the RF signal received from the RF antenna 401.The direct sampling architecture may reduce the need of the number ofanalog devices. The performance of the direct sampling architecture maydepend on the processing capacity of the analog-to-digital converter,i.e., a speed and a number of bits of an analog-to-digital converter.The low noise amplifier 501 may be a low noise amplifier with a highgain. The filter 502 may be configured to filter the amplified RFsignal. The filter 502 may be a low-pass filter or a bandpass filter.

FIG. 6 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure. Asshown in FIG. 6, the analog signal processor 600 may include a low noiseamplifier 601, a down converter 602, a local oscillator 603 and achannel selection filter 604.

The analog signal processor 600 may be a heterodyne receiver. Theheterodyne receiver may convert a received signal (e.g., an amplified RFsignal generated by the low noise amplifier 601) to an intermediatefrequency. The intermediate frequency may satisfy a frequencyrequirement of subsequent components.

The low noise amplifier 601 may be configured to amplify an RF signalreceived by an RF antenna. The amplification may be linear or nonlinear.The local oscillator 603 may be configured to generate a localoscillation signal to be supplied to the low noise amplifier 601.

The down converter 602 may include or may be coupled to a mixer. Themixer may be configured to mix the amplified RF signal and the localoscillation signal. Merely by way of example, the frequency of RF signalmay be expressed as f_(IF) and the frequency of the location oscillationsignal may be expressed as f_(LO). The mixer may generate two signals atf_(LO+) f_(IF) and f_(LO−) f_(IF), respectively. In some embodiments,the down converter 602 may retain and output the signal at f_(LO−)f_(IF) (which is the intermediate frequency). The channel selectionfilter 604 may be configured to filter the output signal of the downconverter 602. In some embodiments, an interference signal may occur at2f_(IF)−f_(LO) (also called an image frequency). The channel selectionfilter 604 may be a bandpass filter to remove the interference signal.

FIG. 7 is a schematic diagram illustrating an exemplary analog signalprocessor according to some embodiments of the present disclosure. Asshown in FIG. 7, the analog signal processor 700 may include a low noiseamplifier 701, a first down converter 702, a first low-pass filter 703,a second down converter 704, a local oscillator 705, a phase-shiftingcircuit 706, and a second low-pass filter 707.

The analog signal processor 700 may be a homodyne receiver. As usedherein, a homodyne receiver may refer to a direct down-convertingreceiver. The carrier frequency of a homodyne receiver (frequency of RFsignal) may be the same as a local frequency (e.g., the frequency of alocal oscillation signal generated by the local oscillator 705).

The homodyne receiver may be related to an orthogonal down-conversion.The orthogonal down-conversion may produce an orthogonal signal I and anorthogonal signal Q. The orthogonal signal I and the orthogonal signal Qmay have same amplitude but different phase. The orthogonaldown-conversion may be realized based on the first down converter 702,the first low-pass filter 703, the second down converter 704, the localoscillator 705, the phase-shifting circuit 706, and the second low-passfilter 707. The low noise amplifier 701 and the local oscillator 705 maybe similar with the low noise amplifier 601 and the local oscillator603, and are not repeated herein. In some embodiments, the localoscillator 705 may generate a local oscillation signal at a frequency ofthe received RF signal. The phase-shifting circuit 706 may shift thelocal oscillation signal by 90 degrees (the amplitude and frequencyremain unchanged) to generate a phase shifted local oscillation signal.

The first down converter 702 may be configured to convert an amplifiedRF signal (e.g., an RF signal amplified by the low noise amplifier 701)to a zero frequency signal based on a phase shifted local oscillationsignal. The method of mixing the phase shifted local oscillation signaland the amplified RF signal is similar to those described in FIG. 0.6and is not repeated herein. An output of the first down converter 702may be input to the first low-pass filter 703 to generate the orthogonalsignal I.

Similarly, the second down converter 704 may be configured to convert anamplified RF signal (e.g., an RF signal amplified by the low noiseamplifier 701) to a zero frequency signal based on a local oscillationsignal. An output of the second down converter 704 may be input to thesecond low-pass filter 707 to generate the orthogonal signal Q.

In some embodiments, the low noise amplifier may be configured with highinput impedance. As used herein, the high input impedance may refer tothe value of input impedance being greater than 500 Ohms, 1000 Ohms, or2000 Ohms. The low noise amplifier with high input impedance may berealized by a field effect transistor (FET), a high electron mobilitytransistor (HEMT), or the like, or a combination thereof.

FIG. 8 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure. As shown, the magnetic resonance RF coil 800 may include anRF antenna 801 and a digital signal processor 802.

The RF antenna 801 may be a loop structure. The digital signal processor802 may include an analog-to-digital sampling circuit. Theanalog-to-digital sampling circuit may be configured to directly convertan analog signal (e.g., an RF signals received by the RF antenna 801) toa digital signal. In some embodiments, the digital signal processor 802may process the sampled digital signal, the processing includingprocedures of signal amplification, frequency conversion, filtering,notch. Based on magnetic resonance RF coil 800, analog components may beomitted, and more space of the RF coil 800 may be saved, allowing thedesigning of the RF coil 800 to be more diversified.

FIG. 9 is a schematic diagram illustrating an exemplary magneticresonance RF coil according to some embodiments of the presentdisclosure. As shown, the magnetic resonance RF coil 900 may include anRF antenna 901, an analog signal processor 902 and an analog-to-digitalconverter 903. The RF antenna 901 may be in a birdcage structure. Theanalog signal processor 902 and the analog-to-digital converter 903 maybe similar to the analog signal processor 403 and the analog-to-digitalconverter 404, respectively, and are not repeated herein.

FIG. 10 is a schematic diagram illustrating an exemplary magneticresonance RF coil 1000 according to some embodiments of the presentdisclosure. As shown, the magnetic resonance RF coil 1000 may include amagnetic resonance RF coil 1001 and a signal processor 1002.

The magnetic resonance RF coil 1001 may be configured to receive RFsignals. The RF signals may be emitted by the imaging object 150. Insome embodiments, the magnetic resonance RF coil 1001 may be an RFvolume coil. The RF volume coil may be in a structure of a birdcage. TheRF volume coil may be placed inside the gantry 145 of the MRI scannerand encompass the entire body of the imaging object 150. In someembodiments, the magnetic resonance RF coil 1001 may be a local coil.The local coil may be configured to encompass a portion of the body ofthe imaging object 150, for example, a head, a wrist, a shoulder, aspine, a foot, or the like, or a combination thereof. The magneticresonance RF coil 1001 may be made of one or more deformable materials.For example, the magnetic resonance RF coil 1001 may be made ofshape-memory alloy. The shape-memory alloy may recover to its originalshape under a recovering condition (e.g., a high temperature, a largestrain). The shape-memory alloy may include silver, cadmium, gold,nickel, titanium, hafnium, copper, zinc, or the like, or any combinationthereof. For another example, the magnetic resonance RF coil 1001 may bemade of deformable conductive materials. The deformable conductivematerials may include metallic materials such as solid metals, alloys,liquid metals, etc. The liquid metals may include mercury, aluminum,cesium, gallium, rubidium, or the like, or any combination thereof. Insome embodiments, the magnetic resonance RF coil 1001 may be asingle-channel coil, for example, a coil with one loop. In someembodiments, the magnetic resonance RF coil 1001 may be a coil arraywith a plurality channels. The number of channels may be 8, 16, 32, 64,etc.

The signal processor 1002 may be configured to process the RF signalsreceived by the magnetic resonance RF coil 901. The processing mayinclude procedures of analog signal amplification, filtering, notch,frequency conversion, analog-to-digital conversion, or the like, or acombination thereof.

The signal processor 1002 may include a matching circuit 1003, anamplifier 1004 and an analog-to-digital converter 1005. The matchingcircuit 1003 may be coupled to the magnetic resonance RF coil 1001 andthe amplifier 1004. The matching circuit 1003 may be configured to matchimpedance of the magnetic resonance RF coil 1001 and impedance of theamplifier 1004. The amplifier 1004 may be configured to amplify thesignal received by the magnetic resonance RF coil 1001. Theanalog-to-digital converter 1005 may be similar to the analog-to-digitalconverter 404, and is not repeated herein.

FIG. 11 is a schematic diagram illustrating an exemplary amplifyingcircuit according to some embodiments of the present disclosure. Asshown, the amplifying circuit 1100 may include an amplifier 1101, afirst adjusting circuit 1102, a second adjusting circuit 1103, a biascircuit 1104, and a third adjusting circuit 1105. The amplifying circuit1100 (or the amplifier 1101) may correspond to the amplifier describedelsewhere in the present disclosure (e.g., low noise amplifier 501, lownoise amplifier 601, low noise amplifier 701, amplifier 1004).

The amplifier 1101 may be configured to amplify an RF signal. Theamplifier 1101 may include a first port A, a second port B, a third portC, and a fourth port D. The first port A may be an input port of theamplifier 1101. The third port C may be an output port of the amplifier1101. The second port B and the fourth port D may be bypass ports of theamplifier 1101. The bypass ports may be configured to distribute poweror bias a circuit.

The first adjusting circuit 1102 may be configured to receive an RFsignal (e.g., an RF signal received by an RF coil). The first adjustingcircuit 1102 may be electrically coupled to an input port of theamplifying circuit 1100 (e.g., the first port A). The first adjustingcircuit 1102 may be configured to adjust a value of an input impedanceof the amplifier 1101. For example, the first adjusting circuit 1102 maybe configured to adjust the value of the input impedance of theamplifier 1101 to a real value (e.g., remove the imaginary part of theimpedance of the amplifier 1101). The first adjusting circuit 1102 mayinclude adjustable components. For example, the first adjusting circuit1102 may include a first resistor R1, a first capacitor C1, and a secondcapacitor C2. The first capacitor C1 and the second capacitor C2 may bevariable capacitors. The capacitance of a variable capacitor may bemechanically controlled or electronically controlled. A mechanicallycontrolled capacitor may include a vacuum variable capacitor, abutterfly capacitor, a split stator variable capacitor, a differentialvariable capacitor, or the like, or a combination thereof. Anelectrically controlled capacitor may include a voltage tuned variablecapacitor, an integrated circuit (IC) variable capacitor, or the like,or a combination thereof.

Similar to the first adjusting circuit 1102, the second adjustingcircuit 1103 may also be electrically connected to an input port A ofthe amplifier 1101. The second adjusting circuit 1103 may includeadjustable components. For example, the second adjusting circuit 1103may include a second resistor R2 and a third capacitor C3 and the thirdcapacitor C3 may be a variable capacitor. The second adjusting circuit1103 may also be configured to adjust the value of the input impedanceof the amplifier 1101 to a real value.

The bias circuit 1104 may be configured to distribute power. The biascircuit 1104 may be electrically connected to a bypass port of theamplifier 1101 (e.g., the fourth port D). The bias circuit 1104 mayinclude a third resistor R3 and a fifth capacitor R5.

The third adjusting circuit 1105 may be configured to receive anamplified RF signal from the amplifier 1101. The third adjusting circuit1105 may be electrically connected to a bypass port of the amplifier1101 (e.g., the fourth port D). The third adjusting circuit 1105 may beconfigured to adjust a value of an output impedance of the amplifier1101. For example, the third adjusting circuit 1105 may be configured toadjust the value of the output impedance of the amplifier 1101 to a realvalue. The third adjusting circuit 1105 may include adjustablecomponents. For example, the third adjusting circuit 1105 may include afourth resistor R4, a fifth resistor R5 and a sixth capacitor C6. Thesixth capacitor C6 may be a variable capacitor.

In some embodiments, the input impedance of the amplifier 1101 may bedetermined based on the first adjusting circuit 1102 and the secondadjusting circuit 1103. The input impedance of the amplifier 1101 may bedetermined by the impedance of the first adjusting circuit 1102 and thesecond adjusting circuit 1103 according to a double terminal networkdescribed in FIG. 12. The value of the input impedance of the amplifier1101 may be expressed in the form of a first complex number. Themagnitude of the imaginary part of the first complex number may be setto 0 by adjusting capacitances of the first capacitor C1, the secondcapacitor C2, and/or the third capacitor C3.

In some embodiments, the output impedance of the amplifier 1101 may bedetermined based on the third adjusting circuit 1105. The outputimpedance of the amplifier 1101 may be determined by impedance of thethird adjusting circuit 1105 according to the double terminal networkdescribed in FIG. 12. The value of the output impedance of the amplifier1101 may be expressed in the form of a second complex number. Themagnitude of the imaginary part of the second complex number may be setto 0 by adjusting the capacitance of the sixth capacitor C6.

This description is intended to be illustrative, and not to limit thescope of the present disclosure. Many alternatives, modifications, andvariations will be apparent to those skilled in the art. The features,structures, methods, and other characteristics of the exemplaryembodiments described herein may be combined in various ways to obtainadditional and/or alternative exemplary embodiments. For example, theadjustable component configured to adjust the input impedance and theoutput impedance of the amplifier 1101 may also be a variable inductor,or a combination of a variable capacitor and a variable inductor. Asanother example, the pulse controller 111, the processing engine 122,and/or the display 123 may be integrated into an MRI console (notshown). Users may set parameters in MRI scanning, control the imagingprocedure, and view the images produced through the MRI console.However, those variations and modifications do not depart the scope ofthe present disclosure.

FIG. 12 is a schematic diagram illustrating an exemplary double terminalnetwork according to some embodiments of the present disclosure. Asshown in FIG. 12, the double terminal network 1200 may include an input1201 and an output 1202.

Merely by way of example, the input 1201 and the output 1202 may beexpressed as:

$\begin{matrix}{\begin{bmatrix}V_{1} \\V_{2}\end{bmatrix} = {\begin{bmatrix}Z_{11} & Z_{12} \\Z_{21} & Z_{22}\end{bmatrix}\begin{bmatrix}l_{1} \\l_{2}\end{bmatrix}}} & (1)\end{matrix}$

where V₁ may denote the voltage of the input 1201, V₂ may denote thevoltage of the output 1202, I₁ may denote the current of the input 1201,I₂ may denote the current of the output 1202, and z₁₁, z₁₂, z₂₁ and z₂₂may denote impedances between the input 1201 and the output 1202.

Merely by way of example, the impedances between the input 1201 and theoutput 1202 may be determined by:

$\begin{matrix}{Z_{11}\overset{def}{=}\left. \frac{V\; 1}{I_{1}} \right|_{I_{2} = 0}} & (2) \\{Z_{12}\overset{def}{=}\left. \frac{V\; 1}{I_{2}} \right|_{I_{1} = 0}} & (3) \\{Z_{21}\overset{def}{=}\left. \frac{V\; 2}{I_{1}} \right|_{I_{2} = 0}} & (4) \\{Z_{22}\overset{def}{=}\left. \frac{V\; 2}{I_{2}} \right|_{I_{1} = 0}} & (5)\end{matrix}$

By measuring the voltage and current of the amplifier, the inputimpedance and the output impedance of the amplifier may be calculated ascomplex values according to the formulae (2) to (5). The variablecomponents (e.g., C1, C2, C3, C6, etc.) in the amplifying circuit 1100may then be adjusted to remove the imaginary part of the compleximpedances.

This description is intended to be illustrative, and not to limit thescope of the present disclosure. Many alternatives, modifications, andvariations will be apparent to those skilled in the art. The features,structures, methods, and other characteristics of the exemplaryembodiments described herein may be combined in various ways to obtainadditional and/or alternative exemplary embodiments. For example, threeor more groups of pixels may be connected to a same signal transmissionboard. However, those variations and modifications do not depart thescope of the present disclosure.

It should be noted that the above description of the embodiments areprovided for the purposes of comprehending the present disclosure, andnot intended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, various variations and modificationsmay be conducted in the light of the present disclosure. However, thosevariations and the modifications do not depart from the scope of thepresent disclosure.

FIG. 13A is a schematic diagram illustrating a conventional magneticresonance coil 1300. As shown in FIG. 13A, the magnetic resonance coil1300 may include an antenna 1301, a phase-shifting circuit 1302, and anamplifier 1303.

The antenna 1301 may be configured to receive an RF signal emitted froman object during an MR scan of the subject. The antenna 1301 may have aloop structure. One or more frequency capacitors for frequency tuningmay be connected in series in the antenna 1301. Merely by way ofexample, as shown in FIG. 13A, a capacitor C7, a capacitor C8, and acapacitor C9 for frequency tuning are connected in series in the antenna1301. The antenna 1301 may further include a matching capacitor Cm foradjusting an input impedance of the antenna 1301.

In FIG. 13A, the total inductance of the antenna 1301 is represented asLoll, and the loss resistance of the antenna 1301 is represented as aload resistance R6. The total inductance Loll may include an inductanceof the antenna 1301. The inductance of the antenna 1301 may beassociated with, for example, the shape of the antenna 1301. The loadresistance R6 may include a resistance of the antenna 1301 itself,resistances of other components in the antenna 1301 (e.g., inductancesof one or more resistors, etc.), and a load resistance of a scannedobject, or the like, or any combination thereof. The total capacitanceof the antenna 1301 may be determined based on the capacitances of thecapacitors C7, C8, C9, and Cm according to Equation (1) as below:

$\begin{matrix}{{\frac{1}{c_{total}} = {\frac{1}{c_{m}} + \frac{1}{c_{7}} + \frac{1}{c_{8}} + \frac{1}{c_{9}}}},} & (1)\end{matrix}$

where C_(total) denotes the total capacitance of the antenna 1301, C₇denotes the capacitance of the capacitor C7, C₈ denotes the capacitanceof the capacitor C8, C₉ denotes the capacitance of the capacitor C9, andC_(m) denotes the capacitance of the capacitor Cm.

The total capacitance and the total inductance of the antenna 1301 mayprovide the antenna 1301 with a specific resonant frequency. When thefrequency of the RF signal emitted from the object matches the resonantfrequency of the antenna 1301, the antenna 1301 may resonate and receivethe RF signal. A resonance condition of the antenna 1301 may berepresented according to Equation (2) as below:

$\begin{matrix}{{{\frac{1}{j\;\omega\; C_{total}} + {j\;\omega\; L_{coil}}} = 0},} & (2)\end{matrix}$

where C_(total) denotes the total capacitance of the antenna 1301,L_(coil) denotes the total inductance of the antenna 1301, ω denotes anangular frequency of an RF excitation pulse emitted toward the object,and j denotes an imaginary unit.

The matching capacitor Cm may be coupled between the antenna 1301 andthe phase-shifting circuit 1302. The matching capacitor Cm may beconfigured to match an impedance of the antenna 1301 and an impedance ofthe amplifier 1303. For example, matching capacitor Cm may adjust aninput impedance of the antenna 1301 to 50 Ohm.

The phase-shifting circuit 1302 may be operably coupled to the antenna1301 and the amplifier 1303. The phase-shifting circuit 1302 may beconfigured to form a conjugate match between a phase of an inputimpedance of the antenna 1301 and a phase of an input impedance of theamplifier 1303 to achieve a purpose of a pre-amp decoupling. Theconjugate match between a phase of an input impedance of the antenna1301 and a phase of an input impedance of the amplifier 1303 refers tothat the imaginary part of the input impedance of the antenna 1301 andthe imaginary part of the input impedance of the amplifier 1303 areopposite to each other.

In the conventional magnetic resonance coil 1300, the capacitance andthe inductance in the antenna 1301 may form a resonance at the operatingfrequency of the antenna 1301. The magnetic resonance coil 1300 mayinclude one or more coil units (or referred to as antenna units). Amutual inductance between different coil units may be generated due to amagnetic field coupling, which may affect the resonance and an inputimpedance of the antenna, and the signal-to-noise ratios (SNRs) of thecoil units. A decoupling mechanism may need to be adopted for themagnetic resonance coil 1300. The decoupling mechanism may include adecoupling between coil units (e.g., a decoupling mechanism usinggeometric overlap, an inductive decoupling mechanism, a capacitivedecoupling mechanism, etc.), a pre-amp decoupling mechanism, or thelike, or any combination thereof.

The decoupling between coil units has some restrictions on the layout ofthe coil units. For example, the decoupling mechanism using geometricoverlap requires that adjacent coil units have a specific overlap area,which limits the flexibility of the layout of the coil units. Merely byway of example, FIGS. 13B and 13C illustrate exemplary conventionalarrangements of coil units with a circular shape. As shown in FIG. 13B,adjacent coil units 1304 with a circular shape need to overlap with eachother for decoupling. If the diameter of each coil unit 1304 is 1 unitlength, the length of the overlapped area between the coil units 1304 is0.25 unit lengths. In a coil array as shown in FIG. 13C, the length ofthe overlapped area between each pair of adjacent coil units 1304 needsto be fixed as 0.25 unit lengths. As shown in FIG. 13D, adjacent coilunits 1305 with a square shape also need to overlap with each other fordecoupling. If the side length of each coil unit 1305 is 1 unit length,the length of the overlapped area between the coil units 1305 is 0.1unit length.

The inductive decoupling mechanism and/or the capacitance decouplingmechanism require that a decoupling inductance pair or a commoncapacitor is formed between adjacent coil units, which results inadditional conductor paths in the antenna loop. The pre-amp decouplingmechanism requires that the amplifier has a low input impedance (e.g.,an input impedance lower than a threshold). However, the low inputimpedance of the amplifier may affect the noise factor and gain index ofthe amplifier, and the input impedance of the amplifier may need to begreater than, for example, 1 Ohm. Therefore, the pre-amp decouplingmechanism has also some limitations. In order to address the problems ofthe conventional magnetic resonance coil, the present disclosureprovides a non-resonant magnetic resonance coil that has an improvedperformance, flexibility, and safety.

FIG. 14 is a schematic block diagram of an exemplary magnetic resonancecoil 1400 according to some embodiments of the present disclosure. Asshown in FIG. 14, the magnetic resonance coil 1400 may include anantenna 1410, an amplifier 1420, and a protective circuit 1430. In someembodiments, the magnetic resonance coil 1400 may include a plurality ofantenna units, and at least one of the antenna units may include one ormore of the components as shown in FIG. 14. It should be noted that themagnetic resonance coil 1400 described herein is merely provided forillustrative purposes, and not intended to limit the scope of thepresent disclosure. The magnetic resonance coil 1400 may find itsapplications in various fields, such as healthcare industries (e.g.,medical applications), security applications, industrial applications,etc. For example, the magnetic resonance coil 1400 may be used forinternal inspections of components including, e.g., flaw detection,security scanning, failure analysis, metrology, assembly analysis, voidanalysis, wall thickness analysis, or the like, or a combinationthereof.

The antenna 1410 may be configured to receive an RF signal emitted froman object (e.g., the imaging object 150) during an MR scan of theobject. For example, during the MR scan of the object, an RF excitationpulse may be emitted toward the object, and the antenna 1410 may beconfigured to receive an RF signal excited by the RF excitation pulsefrom the object. In some embodiments, the antenna 1410 may not resonatewith the RF signal (such antenna 1410 may also be referred to as anon-resonant antenna). Instead, the antenna 1410 may be configured toresonant and receive signals at a wide range of frequencies (broadbandsignals). Merely by way of example, an antenna of a 1.5 T MRI systemthat includes capacitance may resonant at a frequency fixed at, forexample, about 64 MHz. However, the antenna 1410 may resonant at afrequency range, e.g., from 57 MHz to 74 MHz. In some embodiments, theantenna 1410 may be similar to the RF antenna 401, the RF antenna 801,and/or the RF antenna 901 as described elsewhere in this disclosure.

In some embodiments, the antenna 1410 may have an antenna inductance anda load resistance. The antenna inductance may include an inductance ofthe antenna 1410 itself and optionally inductances one or more of othercomponents of the antenna 1410 (e.g., inductances of one or moreinductors, etc.). The load resistance may include a resistance of theantenna 1410 itself, resistances of other components in the antenna 1410(e.g., inductances of one or more resistors, etc.), a load resistance ofthe object, or the like, or any combination thereof. In someembodiments, an input impedance of the antenna 1410 may be determinedaccording to Equation (3) as below:

$\begin{matrix}{{Z_{in} = {R_{total} + {j\;\omega\; L_{coil}}}},} & (3)\end{matrix}$

where Z_(in) denotes the input impedance of the antenna 1410, R_(total)denotes the load resistance of the antenna 1410, L_(coil) denotes theantenna inductance of the antenna 1410, ω denotes an angular frequencyof an RF excitation pulse emitted toward the object during the MR scan,and j denotes an imaginary unit.

The amplifier 1420 may be operably coupled to the antenna 1410 andconfigured to amplify the RF signal. In some embodiments, the amplifier1420 may be similar to an amplifier as described in connection withFIGS. 1-12, such as a low noise amplifier as described in connectionwith FIGS. 5-7.

In some embodiments, an input impedance of the antenna 1410 may besubstantially equal to an input impedance corresponding to an optimalnoise factor of the amplifier 1420. For example, when the inputimpedance of the antenna 1410 is equal to a specific impedance of theamplifier 1420, the noise factor of the amplifier 1420 may be minimizedor optimized. The specific impedance of the amplifier 1420 may bereferred to as the input impedance corresponding to the optimal noisefactor of the amplifier 1420. Additionally or alternatively, theamplifier 1420 may have a high input impedance. As used herein, a highinput impedance refers to an input impedance greater than a thresholdvalue, such as 500 Ohms, 1,000 Ohms, 2,000 Ohms, or the like. If theinput impedance of the antenna 1410 is substantially equal to the inputimpedance corresponding to the optimal noise factor of the amplifier1420 and the amplifier 1420 has a high input impedance value, the seriesimpedance of the antenna 1410 may be high (e.g., higher than a specificseries impedance value) and intensity of the current passing through theantenna 1410 may be small (e.g., smaller than a specific current value).Since a magnetic field coupling between adjacent antenna units isproportional to the intensity of the current passing through the antennaunits, the coupling between adjacent antenna units may be eliminated orreduced. In such cases, the decoupling between adjacent antenna unitsmay be achieved without arranging the antenna units in a specificmanner, which may improve the layout flexibility of the antenna units.

The protective circuit 1430 may be configured to protect the antenna1410 and the amplifier 1420. For example, if the current passing throughthe antenna 1410 and the amplifier 1420 is large (e.g., larger than athreshold current), the antenna 1410 may be hot and cause harm to theobject, and the amplifier 1420 may be damaged. The protective circuit1430 may be configured to protect the antenna 1410 and the amplifier1420 by limiting the current passing through the antenna 1410 and theamplifier 1420.

In some embodiments, the protective circuit 1430 may have an activestate and an inactive state. For example, the protective circuit 1430may be activated when a first actuation condition is satisfied. Forexample, the first actuation condition may include that an RF-inducedvoltage applied to the amplifier 1420 is greater than a first thresholdvoltage, that the current passing through the antenna 1410 exceeds afirst threshold current, the temperature of the magnetic resonance coil1400 exceeds a threshold temperature, or the like, or any combinationthereof. The first actuation condition of the protective circuit 1430may be set manually by a user (e.g., a doctor), or determined accordingto a default setting of the MRI system 100, or determined by aprocessing device (e.g., the processing engine 122) according to anactual need.

In some embodiments, when the protective circuit 1430 is activated, theimpedance of the protective circuit 1430 may be smaller than theimpedance of the antenna 1410. For example, when the protective circuit1430 is activated, the impedance of the protective circuit 1430 may bemuch smaller than the impedance of the antenna 1410, such that theantenna 1410 may remain in a non-resonant state. As used herein, if afirst value is smaller than a second value, and the difference betweenthe first and second values exceeds a specific threshold (e.g., acertain percentage of the second value), the first value may be regardedas being much smaller than the second value. Merely by way of example,the impedance of the protective circuit 1430 may be smaller than 1/10 ofthat of the antenna 1410. Additionally or alternatively, when theprotective circuit is deactivated, the impedance of the protectivecircuit 1430 may be greater than an input impedance of the amplifier1420. In such cases, a greater portion of an RF-induced voltage may beapplied to the protective circuit 1430 than the amplifier 1420, so as toprotect the amplifier 1420.

In some embodiments, the impedance of the protective circuit 1430 may bedetermined based on one or more of an intensity of an RF field at theantenna 1410, an angular frequency of an RF excitation pulse applied tothe object, and the size of the antenna 1410. Merely by way of example,during the MRI scan of the object, a transmitting coil of an MRI devicemay transmit an RF excitation pulse to the object, and the antenna 1410may receive an RF signal emitted from the object that is excited by theRF excitation pulse. The RF excitation pulse may form a space magneticfield, which may further induce an RF-induced voltage applied to themagnetic resonance coil 1400. The RF-induced voltage applied to themagnetic resonance coil 1400 may be determined according to Equation (4)as below:

$\begin{matrix}{{V_{emf} = {\frac{d\;\Phi}{dt} \approx {\omega\;{BA}}}},} & (4)\end{matrix}$

where V_(emf) denotes the RF-induced voltage, Φ denotes a magnetic fluxof the MRI device, t denotes the time, ω denotes an angular frequency ofthe RF excitation pulse, B denotes the intensity of the RF field at theantenna 1410, and A denotes the size of the antenna 410. Normally, theRF-induced voltage may be tens to hundreds of volts. If the amplifier1420 has a high impedance, a large portion of the RF-induced voltage maybe applied to the protective circuit 1430, which may cause damage to theamplifier 1420. Using the protective circuit 1430 may protect theamplifier 1420 from damage.

In some embodiments, the impedance of the protective circuit 1430 may bedetermined based on the RF-induced voltage V_(emf) and a protectivecurrent. For example, the impedance may be determined so that when themagnetic resonance coil 1400 operates, the current passing through themagnetic resonance coil 1400 may be smaller than the protective current.The protective current may be set manually by a user (e.g., a doctor),or determined according to a default setting of the system 100, ordetermined by a processing device (e.g., the processing engine 122)according to an actual need. Merely by way of example, the protectivecurrent may be 0.1 A, 0.05 A, or the like.

In some embodiments, the protective circuit 1430 may include aprotective capacitor, a protective inductor in parallel with theprotective capacitor, and a control device. The control device may beconfigured to actuate the protective circuit 1430 when the firstactuation condition of the protective circuit 1430 is satisfied. Moredescriptions regarding the protective circuit 1430 may be foundelsewhere in the present disclosure. See, e.g., FIGS. 15-18 and relevantdescriptions thereof.

In some embodiments, in a method for controlling the magnetic resonancecoil 1400, each of the antenna 1410 and the amplifier 1420 may becoupled with the protective circuit 1430. During the MR scan of theobject, the protective circuit 1430 may be operated to protect theantenna 1410 and the amplifier 1420.

FIG. 15 is a schematic diagram illustrating an exemplary magneticresonance coil 1500 according to some embodiments of the presentdisclosure. As shown in FIG. 15, the magnetic resonance coil 1500 mayinclude an antenna (not shown in FIG. 15), an amplifier 1420, and aprotective circuit 1430A. The antenna may include an antenna inductance1501 and a load resistance 1502. The antenna including the antennainductance 1501 and the load resistance 1502 may be an exemplaryembodiment of the antenna 1410 as described in connection with FIG. 14.

In some embodiments, the protective circuit 1430A may be capable ofswitching the magnetic resonance coil 1500 between receiving andnon-receiving modes. The protective circuit 1430A may be an exemplaryembodiment of the protective circuit 1430 as described in connectionwith FIG. 14. As shown in FIG. 15, the protective circuit 1430A mayinclude a protective capacitor 1503, a protective inductor 1504 inparallel with the protective capacitor 1503, and a control device. Thecontrol device may include a switch 1505 in series with the protectiveinductor 1504 and a control component 1506 configured to control theswitch 1505. For example, the control component 1506 may include adirect current (DC) controller. The switch 1505 may be configured toactuate the protective circuit 1430A when the first actuation conditionis satisfied. The switch 1505 may include, for example, a radiofrequency (RF) diode, a PIN diode, a micro-electromechanical system(MEMS) switch, or a field-effect transistor (FET) switch, etc. Merely byway of example, when the switch 1505 is closed, the protective circuit1430A may be activated, and current may pass through the protectivecapacitor 1503 and the protective inductor 1504. The activation of theprotective circuit 1430A may cause the magnetic resonance coil 1500 toswitch from a non-receiving mode to a receiving mode.

In some embodiments, the impedance of the protective capacitor 1503 maybe smaller than (e.g., much smaller than) the impedance of the antennainductance 1501, for example, the impedance of the protective capacitor1503 may be smaller than 1/10 of the impedance of the antenna inductance1501. In such cases, the antenna 1410 may maintain a non-resonant statewhen the protective circuit 1430A is deactivated. The deactivation ofthe protective circuit 1430A may cause the magnetic resonance coil 1500to switch from a receiving mode to a non-receiving mode. When the firstactuation condition is satisfied, the control device may actuate theprotective circuit 1430A, and the impedance of the protective circuit1430A may be determined according to Equation (5) as below:

$\begin{matrix}{{Z_{p} = \frac{\left( {\omega\; L_{p}} \right)^{2}}{r_{p}}},} & (5)\end{matrix}$

where Z_(p) denotes the impedance of the protective circuit 1430A, L_(p)denotes an inductance of the protective inductor 1504, r_(p) denotes aload resistance of the protective circuit 1430A, and ω denotes theangular frequency of the RF excitation pulse.

In some embodiments, the impedance of the protective circuit 1430A maybe greater than the input impedance of the amplifier 1420, so that theRF-induced voltage may be mainly concentrated at the ends of theprotective circuit 1430A and the amplifier 1420 may be protected.

FIG. 16 is a schematic diagram illustrating an exemplary magneticresonance coil 1600 according to some embodiments of the presentdisclosure. The magnetic resonance coil 1600 may be similar to themagnetic resonance coil 1500 as described in connection with FIG. 15,except that the magnetic resonance coil 1600 includes a protectivecircuit 1430B different from the protective circuit 1430A of themagnetic resonance coil 1500.

As shown in FIG. 16, the protective circuit 1430B may include theprotective capacitor 1503, the protective inductor 1504 in parallel withthe protective capacitor 1503, and a control device 1601. The controldevice 1601 may include a first pair of anti-parallel diodes in serieswith the protective inductor 1504. The first pair of anti-paralleldiodes may be configured to actuate the protective circuit 1430B whenthe first actuation condition is satisfied. For example, when thecurrent passing through the antenna exceeds a threshold current, thefirst pair of anti-parallel diodes may be powered on and the protectivecircuit 1430B may be activated.

FIG. 17 is a schematic diagram illustrating an exemplary magneticresonance coil 1700 according to some embodiments of the presentdisclosure. The magnetic resonance coil 1700 may be similar to themagnetic resonance coil 1500, except that the magnetic resonance coil1700 may further include a sub-protective circuit 1701 configured toprotect the amplifier 1420.

As shown in FIG. 17, the sub-protective circuit 1701 may include asecond pair of anti-parallel diodes in parallel with the amplifier 1420.For example, the second pair of anti-parallel diodes may be configuredto actuate the sub-protective circuit 1701 when a second actuationcondition is satisfied. For example, the second actuation condition mayinclude that an RF-induced voltage applied at both ends of the amplifier1420 is greater than a second threshold voltage, that the currentpassing through the amplifier 1420 exceeds a second threshold current,etc. The second actuation condition of the sub-protective circuit 1710may be set manually by a user (e.g., a doctor), or determined accordingto a default setting of the MRI system 100, or determined by aprocessing device (e.g., the processing engine 122) according to anactual need. In some embodiments, the second actuation condition may bethe same as or different from the first actuation condition of theprotective circuit 1430A.

It should be noted that the above descriptions of FIGS. 14-17 are merelyprovided for the purposes of illustration, and not intended to limit thescope of the present disclosure. For persons having ordinary skills inthe art, multiple variations and modifications may be made under theteachings of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure. Insome embodiments, a magnetic resonance coil (e.g., one or more of themagnetic resonance coils 1400, 1500, 1600, and 1700) may further includeone or more additional components and/or one or more components of themagnetic resonance coil described above may be omitted. Additionally oralternatively, two or more components of the magnetic resonance coil maybe integrated into a single component. A component of the magneticresonance coil may be implemented on two or more sub-components. Merelyby way of example, the magnetic resonance coil may further include oneor more components as described in connection with FIGS. 1-13, such asan adjusting circuit coupled to the amplifier 1420 configured to adjustthe magnitude of the imaginary part of an impedance of the amplifier1420, a matching circuit coupled between the antenna 1410 and theamplifier 1420, a heterodyne receiver or a homodyne receiver, or thelike, or any combination thereof.

In some embodiments, the protective circuit 1430 may be modifiedaccording to an actual need. For example, the protective circuit 1430Bof the magnetic resonance coil 1600 may further include thesub-protective circuit 1701. As another example, the protective circuit1430 may include any components that can actuate the protective circuit1430 when an auction condition is satisfied. In some embodiments, amagnetic resonance coil may include a plurality of protective circuits.

FIG. 18A is a schematic diagram illustrating an exemplary magneticresonance coil 1800A including a plurality of antenna units according tosome embodiments of the present disclosure. FIG. 18B is a schematicdiagram illustrating another exemplary magnetic resonance coil 1800Bincluding a plurality of antenna units according to some embodiments ofthe present disclosure. The magnetic resonance coil 1800A may include aplurality of antenna units, each of which includes the antenna 1410, theamplifier 1420, and the protective circuit 1430. The magnetic resonancecoil 1800B may be similar to the magnetic resonance coil 1800A, exceptthat the overlap area between adjacent antenna units of the magneticresonance coil 1800B is larger than that of the magnetic resonance coil1800A.

Since the antenna 1410 of each antenna unit is non-resonant, the currentpassing through each antenna unit is small (e.g., smaller than athreshold current), and the amplitude of the space electric field andthe magnetic field formed by each antenna unit is relatively small. Insuch cases, the decoupling between adjacent antenna units may be reducedor eliminated, thereby obviating the need for adopting a decouplingmechanism using geometric overlap. An antenna unit may be arranged atany position relative to its adjacent antenna unit, and the magneticresonance coils 1800A and 1800B may have a flexible layout. In addition,the magnetic resonance coils 1800A and 1800B may operate normally evenif they are deformed during an MR scan.

In some embodiments, a magnetic resonance coil (e.g., 1800A or 1800B)may include an elastic base, and the central points of the antenna unitsmay be fixed on the elastic base. During an MR scan of an object, theelastic base may be deformed to conform to the body shape of the objectso that the antenna units may get close to the object. In someembodiments, at least one antenna unit of the magnetic resonance coilmay be movable. For example, an antenna unit may be able to moverelative to its adjacent antenna unit, and the overlapped area betweenthe antenna unit and its adjacent antenna unit may be adjusted.

It should be noted that the examples illustrated in FIGS. 18A and 18Bare merely provided for the purposes of illustration, and not intendedto limit the scope of the present disclosure. For persons havingordinary skills in the art, multiple variations and modifications may bemade under the teachings of the present disclosure. However, thosevariations and modifications do not depart from the scope of the presentdisclosure. In some embodiments, an antenna 1410 may have any shape andsize. For example, the antenna 1410 may be non-resonant and have a loopstructure or a birdcage structure. As another example, the antenna 1410may be a transverse electromagnetic (TEM) coil, such as a dipoleantenna, a microstrip transmission line, or the like, or any combinationthereof. In some embodiments, a magnetic resonance coil may include anycount of antenna units.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and/or “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art, aspects ofthe present disclosure may be illustrated and described herein in any ofa number of patentable classes or context including any new and usefulprocess, machine, manufacture, or composition of matter, or any new anduseful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “block,” “module,” “engine,” “unit,” “component,” or“system.” Furthermore, aspects of the present disclosure may take theform of a computer program product embodied in one or more computerreadable media having computer readable program code embodied thereon.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a frame wave. Such a propagated signal may takeany of a variety of forms, including electro-magnetic, optical, or thelike, or any suitable combination thereof. A computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that may communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device. Program code embodied on acomputer readable signal medium may be transmitted using any appropriatemedium, including wireless, wireline, optical fiber cable, RF, or thelike, or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object-oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB. NET,Python or the like, conventional procedural programming languages, suchas the “C” programming language, Visual Basic, Fortran 2008, Perl, COBOL2002, PHP, ABAP, dynamic programming languages such as Python, Ruby andGroovy, or other programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider) or in a cloud computing environment or offered as aservice such as a Software as a Service (SaaS).

Furthermore, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations therefore, is notintended to limit the claimed processes and methods to any order exceptas may be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful embodiments of the disclosure, it is to be understoodthat such detail is solely for that purpose, and that the appendedclaims are not limited to the disclosed embodiments, but, on thecontrary, are intended to cover modifications and equivalentarrangements that are within the spirit and scope of the disclosedembodiments. For example, although the implementation of variouscomponents described above may be embodied in a hardware device, it mayalso be implemented as a software only solution—e.g., an installation onan existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the present disclosure, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure aiding in theunderstanding of one or more of the various inventive embodiments. Thismethod of disclosure, however, is not to be interpreted as reflecting anintention that the claimed object matter requires more features than areexpressly recited in each claim. Rather, inventive embodiments lie inless than all features of a single foregoing disclosed embodiment.

In some embodiments, the numbers expressing quantities of ingredients,properties, and so forth, used to describe and claim certain embodimentsof the application are to be understood as being modified in someinstances by the term “about,” “approximate,” or “substantially.” Forexample, “about,” “approximate,” or “substantially” may indicate ±20%variation of the value it describes, unless otherwise stated.Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the application are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable.

Each of the patents, patent applications, publications of patentapplications, and other material, such as articles, books,specifications, publications, documents, things, and/or the like,referenced herein is hereby incorporated herein by this reference in itsentirety for all purposes, excepting any prosecution file historyassociated with same, any of same that is inconsistent with or inconflict with the present document, or any of same that may have alimiting affect as to the broadest scope of the claims now or laterassociated with the present document. By way of example, should there beany inconsistency or conflict between the description, definition,and/or the use of a term associated with any of the incorporatedmaterial and that associated with the present document, the description,definition, and/or the use of the term in the present document shallprevail.

It is to be understood that the embodiments of the application disclosedherein are illustrative of the principles of the embodiments of theapplication. Other modifications that may be employed may be within thescope of the application. Thus, by way of example, but not oflimitation, alternative configurations of the embodiments of theapplication may be utilized in accordance with the teachings herein.Accordingly, embodiments of the present application are not limited tothat precisely as shown and described.

In closing, it is to be understood that the embodiments of theapplication disclosed herein are illustrative of the principles of theembodiments of the application. Other modifications that may be employedmay be within the scope of the application. Thus, by way of example, butnot of limitation, alternative configurations of the embodiments of theapplication may be utilized in accordance with the teachings herein.Accordingly, embodiments of the present application are not limited tothat precisely as shown and describe.

1. A magnetic resonance coil, comprising: an antenna configured toreceive a radio frequency (RF) signal emitted from an object, whereinthe antenna does not resonate with the RF signal; and an amplifieroperably coupled to the antenna configured to amplify the RF signal.2-3. (canceled)
 4. The magnetic resonance coil of claim 1, furthercomprising a protective circuit configured to protect the antenna andthe amplifier. 5-20. (canceled)
 21. A magnetic resonance coil,comprising: an antenna configured to receive a radio frequency (RF)signal emitted from an object; and a signal processor coupled to theantenna and configured to process the RF signal to generate a processedsignal, wherein the antenna is configured without capacitive elements onconductive materials.
 22. The magnetic resonance coil of claim 21,wherein the antenna is made of one or more deformable conductivematerials.
 23. The magnetic resonance coil of claim 22, wherein the oneor more deformable conductive materials include an elastic metalmaterial or a liquid metal material.
 24. The magnetic resonance coil ofclaim 23, wherein the elastic metal material or the liquid metalmaterial includes a nonmagnetic material.
 25. The magnetic resonancecoil of claim 21, wherein the antenna is configured to resonant andreceive signals at a wide range of frequencies.
 26. The magneticresonance coil of claim 21, wherein the antenna is configured toresonant at a frequency range from 57 MHz to 74 MHz.
 27. The magneticresonance coil of claim 21, wherein the antenna only includes an antennainductance and a load resistance.
 28. The magnetic resonance coil ofclaim 21, wherein the signal processor includes a matching circuit andan analog signal processor, the matching circuit is electricallyconnected to the non-resonant antenna and configured to match animpedance of the non-resonant antenna and an impedance of the analogsignal processor.
 29. The magnetic resonance coil of claim 28, whereinthe matching circuit is a broadband matching circuit.
 30. The magneticresonance coil of claim 28, wherein the analog signal processor includesan amplifier coupled to the non-resonant antenna and configured toamplify the RF signal.
 31. The magnetic resonance coil of claim 30,wherein the amplifier includes a high input impedance configured toreceive and output differential signals.
 32. The magnetic resonance coilof claim 30, wherein the amplifier includes a direct samplingarchitecture configured to directly sample the RF signal received fromthe RF antenna.
 33. The magnetic resonance coil of claim 30, wherein theanalog signal processor is a heterodyne receiver.
 34. The magneticresonance coil of claim 30, wherein the analog signal processor furtherincludes a local oscillator, a down converter coupled to a mixer, and achannel selection filter, the local oscillator is configured to generatea local oscillation signal to be supplied to the amplifier, the mixer isconfigured to mix the amplified RF signal and the local oscillationsignal, and the channel selection filter is configured to filter anoutput signal of the down converter.
 35. The magnetic resonance coil ofclaim 30, wherein the analog signal processor is a homodyne receiver.36. The magnetic resonance coil of claim 30, wherein the analog signalprocessor further includes a first down converter, a first low-passfilter, a second down converter, a local oscillator, and a secondlow-pass filter.
 37. The magnetic resonance coil of claim 36, whereinthe local oscillator is configured to generate a local oscillationsignal at a frequency of the RF signal.
 38. The magnetic resonance coilof claim 1, wherein the antenna only provides an antenna inductance anda load resistance.